1. Technical Field of the Invention
The invention relates to a technology for an umber paint to be coated on surfaces of bulbs to be used in lamps of vehicles and, more particularly, to an umber paint excellent in transparency and heat resistance without bringing about environmental pollution, yet suited to coating glass surfaces of bulbs to be used in turn signal lamps. Further, the present invention related to an improved technology of bulbs coated with the umber paint.
2. Related Prior Art
There are furnished turn signal lamps at the front, rear and both sides of vehicles such as cars. The turn signal lamps are used when a vehicle starts, changes running routes, turns left or right. The turn signal lamp changes a white light issued from a bulb (such as an incandescent lamp provided within the lamp) into an umber light (orange-colored light), and turns on and off an umber light so as to let pedestrians or other cars know a driving course.
There are known several methods of changing to umber color the lights issued from bulbs, which methods have conventionally been employed on turn signal lamps. A first prior art furnishes caps (umber caps) of an umber color to bulbs of a transparent monochrome color. A second prior art directly coats a colored paint (coating agent, containing chromium based pigment) on the glass surfaces of the bulbs.
The above-described prior art has been developed for coloring front lenses of turn signal lamps, so that when strong lights as a brilliant sun ray shine on the lamps, it is easier to see when the monochrome bulbs turn on and off. However, even with such coloration, it is difficult for following cars to recognize when the bulbs are on and when they are off.
1. Problems Solved by the Invention
However, in the prior art, there are still technical problems to be solved.
In the first prior art, since the umber caps are added to parts of the turn signal lamps, the number of parts increases thereby increasing cost. Also, because a holding structure is necessary for mounting the umber caps, structural limitations increase.
The second prior art has a basic problem in that the heat resistance of the coated film formed on the bulb surface is low. Further, since colored paints containing chromium-based pigment are used, and because cadmium is added to the paint for increasing its heat resistance, environmental problems occur.
Therefore, it is an object of the present invention to offer an umber paint that is excellent in transparency and heat resistance without bringing about environmental pollution. It is another object of the invention to provide bulbs of high quality coated with the umber paint, and turn signal lamps of high visibility.
For accomplishing the above and other objects, the following aspects of the invention are employed.
A first aspect of the invention is to offer an umber paint, for a turn signal, containing at least a red pigment and a yellow pigment, wherein the yellow pigment comprises acetylacetone metal chelate.
This aspect abolishes employment of conventional indoline-based, Chinacdoline-, metal complex azo-, transparent red oxide yellow-, or condensed azo-based pigments, which were used as a yellow pigment for mixing with a red pigment for making an umber color. Instead this aspect of the invention uses a new pigment composed of acetylacetone metal chelate.
The acetylacetone metal chelate is a chemical compound in which acetylacetonate ligand is chelate-ligated in a metallic ion as an iron. Because this acetylacetone metal chelate is especially excellent in transparency, it easily shields a light issued from a bulb (filament), does not lower brightness, and smoothens out heat dissipation.
In the umber paint for turn signal lamps, according to a second aspect of the invention, for the red pigment set forth in the first aspect there is used a red iron oxide pigment (xcex1a-Fe2O3). Further, the second aspect defines the weight ratio of the red iron oxide pigment to the yellow pigment comprising acetylacetone metal chelate as being within the range of from 1:1.5 to 1:2.8.
According to this aspect, in the X and Y coordinates of XYZ color system, conditions of chromaticity expressed by the following formulae can be satisfied
0.398xe2x89xa6yxe2x89xa60.429xe2x80x83xe2x80x83(I) 
Zxe2x89xa60.007xe2x80x83xe2x80x83(II) 
x+y+z=1xe2x80x83xe2x80x83(III). 
If these conditions are not satisfied, the chromaticityxe2x80x94when lighting the turn signal lampsxe2x80x94does not satisfy the European standards (ECE Reg. No. 37), which are more strict than the North American standards (SAE Standards of Chromaticity J 588). Incidentally, x, y, z of the above formulae (I) to (III) indicate the changing values of the chromaticity coordinate in response to X, Y, Z of three excitation values in colors of a light source.
A third aspect of the invention adds zirconium oxychloride, as a dispersing agent, to the umber paint for turn signal lamps as set forth in either one of the first and second aspects. The third aspect of the invention mainly is aimed at increasing the quantity of light by improving transparency. Because zirconium oxychloride functions to increase the paint transparency, heat dissipation within the bulb is smoother. And it is assumed that the more smooth heat dissipation contributes to an improvement of the bulb""s heat resistance.
A fourth aspect of the invention is a bulb that is coated on the surface thereof with the umber paint as set forth in any one of the first to third aspects.
Using the bulb obtained by this aspect, a turn signal lamp achieves excellent endurance (heat resistance) and improved visibility.
A fifth aspect of the invention further defines the bulb, as set forth in the fourth aspect, as having a film thicknessxe2x80x94of the umber paint coated on the bulb surfacexe2x80x94in the range of 1.5 xcexcm to 3.0 xcexcm.
When the film thickness is less than 1.5 xcexcm, a chromaticity satisfying various standards cannot be provided. On the other hand, when the film thickness is more than 3.0 xcexcm, cracks easily occur in a coated film. Thus, according to the present aspect, it is possible both to secure a proper chromaticity, and to avoid cracks.
In a sixth aspect of the invention, the bulb set forth in either one of the fourth and fifth aspects includes luminous parts that are double filaments.
According to this aspect, it is possible to secure a desired endurance (heat resistance) and visibility, even in bulbs of double filaments wherein there is an increased temperature when turned on. Accordingly, turn signal lamps furnished with the inventive bulbs can maintain a high luminous intensity of orange colored light (issued from the bulbs), and can have excellent visibility.
As mentioned above, since the umber paint of the present invention has excellent transparency and heat resistance, without bringing about environmental pollution, the invention is technically significant. When embodied as a bulb coated with the umber paint, the present invention improves the quality of a turn signal lamp furnished with this bulb and, in turn, heightens the visibility of the turn signal lamp. Thus, the invention has technical meaning in increasing traffic safety of vehicles.